Pitcher take a legal position on the plate with the pivot foot heel-half of her foot on the plate and the toes-half of her foot in the dirt.
As part of her motion, she raises her hands and brings them down into the forward motion.
The pivot heel also raises and comes back down with no movement in any direction and the toes still in the same spot. The pivot foot does not move forward or sideways until dragged by the stride and never leaves the ground.

I ruled it is legal as the pivot foot does not actually move or leave the plate.
There are 2 cases in the book which seem to confirm, 6.1.2 b & c.

Please tell me your agreement; or disagreement/why.

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Officiating takes more than OJT.
It's not our jobs to invent rulings to fit our personal idea of what should and should not be.